The Stovebolt Site Forums The Parking Lot Big Bolts 261 to 350 Swap Bellhousing Options

I picked up a 57 6100 with a locked up 261 and 4 speed in it. I am picking up a 350 today to drop in this weekend and just realized after a little research the 261 bellhousing is a no go for the 350. I am doing a weld in crossmember to side mount the motor. What options do I have for bellhousings that will work with the bellhousing crossmember? Are there a broad range of options or will I have to modify the crossmember to get a wider range of bellhousings to work?
Thanks!
Aaron

Hy Wvgearhead, you can use an iron bellhousing from a 1955 - 59 or 63 - 68 Chevrolet truck originally equipped with a V8 engine, hope that helps.

Thanks 3B. What problems would I run into with a bellhousing from a 67 C10 that has a 250 straight six? This is the only one I have found local thus far.
Thanks!

Hy Wvgearhead, that bellhousing should bolt up and if it's an iron one the only problem might be the size of the center hole, I'm not sure if the transmissions of that era had the same diameter of transmission front bearing retainer. What transmission was behind that bellhousing?

My 57 has a 4 speed. The 67 C10 is a 2wd with a 3 speed. There may have been 2 different types on either of those years but I dont know anymore detail at the moment.

Why aren't you using the '57 V8 front motor mount chicken legs? It will save you from having to align everything before drilling the frame...all of the needed holes are there from the factory taking the guess work out.

https://www.classicparts.com/1955-59-Original-V-8-Conversion-Set/productinfo/79-375/

I think the 3-speed bell housing center hole is smaller than the 4-speed hole.

Mike B

Mike, I was going to go that route at first. The block I am picking up doesn't have threaded holes in the front (or at least my buddy didn't think it did) Also I am not 100% sure how good the tranny is. I doubt anything could be wrong with it but in the case I would need to transplant something else, I figured side motor mounts would give me more options. Which could possibly lead to building a crossmember but being able to put something else in if need be..... probably should have went that route. Been quicker.
Prepare for a dumb question. Can I cut the center hole out bigger? I know cast is tough to deal with...

Welcome Wvgearhead!
How bad is your 261? Do you think it is salvageable? What are your plans for it? Lots of folks looking for one if it could be saved.

Easy enough to bore the bellhousing hole out to 5.125" with the proper tools. Drill press/NO. Lathe, awkward to set up. Vertical mill(Bridgeport) with dial indicator to set-up/excellent.

Ed

If the 261 block doesn't have any gaping holes or big freeze cracks in it, don't scrap it! Somebody will come along who's willing to take it, and maybe even pay you for it!
Jerry

If the 4 speed in your '57 is original, it's an sm420. Those bellhousings have a 4 11/16 bore for the front bearing retainer.

The sm465 that came along in '73 had the bigger 5 1/8 front bearing retainer.

All the three speeds I've seen had the same 4 11/16 front bearing retainer as the sm420.

When I swapped my 3 speed for an sm420, it was bolt in. No mods to the bellhousing were needed

Thanks! That's a huge help!

As for the old motor, I don't see any cracks in the block. My buddy's dad is interested in my 261, but I haven't really talked much about it.

SM465 came out in '68. As I recall early versions had the 4 11/16 retainer. Someone can chime in on that.

One can always turn down a retainer or bore out a bellhousing.

Ed

Guys, I am looking at using a bellhousing out of a 72 c10. I assume the fly wheel off of the 261 won’t work on a 70s 350. Is that correct? Also assuming that correct and buying a sbc flywheel, is the pressure plate/clutch setup(from the 261) compatible with sbc flywheel?
Thanks again!

Hy Wvgearhead, no the 261 flywheel will not bolt up to a small block Chev V8. Depending on what size clutch you have you should be able to find a flywheel that will allow you to bolt it to, hope that helps.

Buy a flywheel and clutch for the 350 and a disc that fits the transmission spline which is the correct diameter for the clutch. Watch the clearance between the disc center and the clutch/flywheel. The pilot bearing in the crankshaft must be chosen to fit the pilot shaft of the transmission. The bell housing must be the correct depth so the pilot shaft fits the pilot bearing. Some pilot bearings can be modified or a special one made to fit. The clutch, throwout bearing, fork and bell house must all mate together. There are several different combinations available, the best place to figure out what exactly you need is a clutch specialty shop (that rebuilds clutches) or a custom shop that builds these combinations on a regular basis.